A consortium of Japanese oil companies has bought a 20% stake in Royal Dutch/Shell's deal to develop oil fields in Iran.

The consortium, led by Japanese Petroleum Exploration (Japex), was set up with the specific aim of taking part in the project to develop the Soroosh and Nowrooz oil fields.

Shell said it had agreed the $800m (£500m) development three years ago and was continuing to look for other opportunities in the area.

Members of the consortium described the venture as a 'buy back' project, whereby companies are paid in oil in return for their investment.

Key figures

Japex is the major shareholder in the Japanese consortium, with a holding of almost 42%.

It is followed by Japanese National Oil (JNOC), the state-run group with a 33% holding and INPEX with a 25% stake.

JNOC said it was investing $13.8m in the deal and that an Iranian oil firm - Oil Industry Engineering and Construction - had also bought into the project although it would not reveal the size of its investment.

The Soroosh and Nowrooz fields have estimated reserves of over 1bn barrels and are being developed by Shell under an agreement with the National Iranian Oil Company.

But Shell denied the involvement of foreign partners was the start of its exit policy from Iran.

"The farm-out is purely a commercial arrangement set in motion three years ago," said Robert Weener, chief executive of Shell in Iran.

Tapping further

Japan Petroleum and INPEX are also leading a separate consortium looking to develop Iran's Azadegan oil field, believed to be one of the largest in the world.

In 2000, Teheran gave Japanese firms exclusive negotiating rights for Azadegan.

Azadegan, along with the Kashagan oil field in Kazhakhstan, is one of the few untapped oil fields left in the world.

Gaining a foothold in Iran's oil production would be a major boost for Japan, which currently imports about 85% of its oil from the Middle East.